On evaluating stent-artery interaction in abdominal aortic stent grafting: an in-depth analysis of longitudinal and pulsatility related behavior

Nowadays, endovascular aneurysm repair (EVAR) is primarily used to treat abdominal aortic aneurysm (AAA). EVAR has an evident perioperative survival benefit compared to open repair. However, long-term results of EVAR are shown to be similar to that of open repair, which is related to the relatively high rate of reintervention after EVAR.
The outcome of EVAR largely depends on how a stent-graft is used and is able to resist or adapt to the dynamic endovascular environment. Hence, knowledge of the behavior of implanted stent-grafts is essential to allow for liable durability tests and to design more durable devices. The objective of this thesis is to develop, validate and apply methods to broaden our understanding of in-vivo stent-graft behavior.
Meticulous image processing methods involving image registration, model-based stent-graft segmentation, and centerline extraction were developed, validated, and applied. The longitudinal and cardiac-pulsatility induced behavior of an infrarenal fixating stent-graft with a nitinol self-expanding stent-ring design was investigated in detail. Through the establishment of a prospective study electrocardiogram (ECG)-gated computed tomography (CT) data of eventually 15 patients were gathered through a study protocol with a 2-years follow-up period. Predominantly, this work focused on the proximal double stent-ring in the aortic neck; the factor known to be crucial for durable exclusion of the aneurysm. Secondly, the stent-graft’s limb configuration was investigated to help better understand the emergence of limb occlusion. Furthermore, the proximal stability of a sac-anchoring endosystem in combination with chimney grafts (chEVAS) was evaluated during the cardiac cycle using 11 retrospectively gathered ECG-gated CT angiography scans.
The developed and applied methods enable to visualize and quantify in vivo stent-graft response and improve our understanding of the ongoing interplay of the device and the vessel. The work presented in this thesis contributes to the foundation of informed shared decision making in device selection, sizing, positioning, and surveillance, and the prediction of failure in an early stage. Moreover, this work supports the development of sound preclinical tests to introduce EVAR devices that well fit and can better endure the endovascular environment. The presented methods can be readily utilized for different endovascular devices, including devices with branches, fenestrations, and chimney grafts.